A flat flexible cable is a common connecting wire between electric devices. It is advantageous to be easily and reversibly bent and stretched in a narrow and crowded space. For example, in a flatbed image scanner, the moving-around carriage containing therein optical and photoelectric devices is connected with the circuit board through a flat flexible cable. Please refer to FIGS. 1(a) and 1(b) which are a top and a cross-sectional side views, respectively, schematically showing the arrangement of a flat flexible cable in a flatbed image scanner. The flatbed scanner includes an upper cover (not shown) and a lower housing 10. In the lower housing, a carriage 11 containing therein optical and photoelectric devices, a driving device 12 consisting of a motor and gear set 121 and a rail set 122, a circuit board 13 for processing electric signals received from the carriage 11, and a flat flexible cable 14 connecting the carriage 11 with the circuit board 13 are covered with a transparent scanning platform 15 for placing thereon the object to be scanned. The carriage 11 is moved by the motor and gear set 121 along the rail set 122 to pass by the scanned object, e.g. a document, film or picture, so as to realize the image data of the document or picture.
Please refer to FIG. 2(a), which is a schematic cross-sectional diagram showing the structure of a conventional flat flexible cable. The flat flexible cable 14 includes a flexible copper foil 141, an insulating wrapper 142 made of a flexible plastic, and a strengthening plate 143 made of a rigid plastic. The insulating wrapper 142 surrounds the copper foil 141 with two ends of the copper foil 141 exposed for electric contact with the carriage 11 and the circuit board 13, respectively. The strengthening plate 143 is mounted onto the end portion of the flat flexible cable 14 to facilitate the insertion of the exposed copper foil into the connecting slot (not shown) of the carriage 11 or the circuit board 13.
The configuration of the flat flexible cable 14 changes with the movement of the carriage 11 along a scanning direction. Before a scanning operation begins, the carriage 11 stands beside the circuit board 13 so that the flat flexible cable 14 is bent at around the middle point thereof. With the movement of the carriage 11 away from the circuit board 13, the bent point also advances. As is known to those skilled in the art, the flat flexible cable is made of light and flexible material such as plastic or rubber so that the bent portion ascends relative to the unbent portion due to the flexible property thereof. The bent portion may undesirably rise up to the inner surface of the platform 15 that is made of glass so as to be subject to abrasion. As shown in FIG. 2(b), abrasion is likely to occur in the bent portion due to the contact of the flat flexible cable 14 with the transparent platform 15. Especially for an image scanner having reduced thickness or using a contact image sensor (CIS) as an image pickup device which requires close contact with the document placed on the platform 15, the flat flexible cable 14 has great chance to keep in contact with the inner surface of the platform 15. The dropped chips resulting from the abrasion may smear the platform 15 and adversely affect the scanning quality.